TPS563257: What is the purpose of R3 resistor in Figure 8-1 schematic of TPS563257 datasheet.

Hi Gautam,

Thank you very much for your reply.

Could I ask you a few additional questions as the below?

Q1.
Is it correct to understanding that R3 is a resistor to prevent damage to the IC from surges?

Q2.
If R3 is not inserted, will TPS563257 be damaged when a surge is come to output line? 

Q3.
Does R3 also have the role of filtering noise coming in from outside?

Thank you again and best regards,
Kazuya.

Kazuya Nakai59 said:

Is it correct to understanding that R3 is a resistor to prevent damage to the IC from surges?

Yes

Kazuya Nakai59 said:

If R3 is not inserted, will TPS563257 be damaged when a surge is come to output line? 

Yes, a possibility esp. depending on output system behavior.

Kazuya Nakai59 said:

Does R3 also have the role of filtering noise coming in from outside?

To a certain extent. 

Regards,

Gautam

Hi Gautam,

Thank you very much for your reply.

Could I ask you the following questions?

Q1.
I think it's rare to see a standard circuit with R3.
Why is R3 needed in the case of the TPS56257?
Is the FB pin of the TPS56257 vulnerable to surge currents?

Q2.
Is R3's main purpose surge protection, not noise filtering?

Q3.
What is the basis for R3 being 51 Ω?

Thank you again and best regards,
Kazuya.

Kazuya Nakai59 said:

I think it's rare to see a standard circuit with R3.
Why is R3 needed in the case of the TPS56257?
Is the FB pin of the TPS56257 vulnerable to surge currents?

This is recommended but majority of customers avoid it in their applications. R3 is hardly used. 

Kazuya Nakai59 said:

Is R3's main purpose surge protection, not noise filtering?

Majorly noise filtering and less for surge protection. 

Kazuya Nakai59 said:

What is the basis for R3 being 51 Ω?

Optimized value as per our EVM. There's not theoretical value to arrive to 51E. 

Regards,

Gautam

Hi Gautam,

Thank you very much for your support.

Please let me confirm.
Which is correct, your 1'st and 2'nd reply?

Your 1'st reply
>It serves as a current limiter and provide surge protection. 

2'nd reply
>Majorly noise filtering and less for surge protection. 

Your reply would be much appreciated.

Thank you again and best regards,
Kazuya.